SCA2 is an autosomal dominant, neurodegenerative disorder that affects the cerebellum and other areas of the central nervous system.
It has recently been discovered that the causative genes of five neurodegenerative diseases including dentatorubral-pallidoluysian atrophy (DRPLA) have more CAG repeats than the normal genes. That is, the numbers of CAG repeats in the causative genes of the neurodegenerative diseases are 37 to 100, while those in the normal genes are less than 35.
It has been suggested that the causative gene of SCA2 has an increased number of CAG repeats (Trottier, Y. et al. Nature, 378, 403-406 (1995)). However, since the causative gene of SCA2 has not been identified, and since its nucleotide sequence has not been determined, SCA2 cannot be diagnosed by a genetic assay.